Solution styrene butadiene rubbers are synthetic products consisting of butadiene and styrene units made by solution polymerization method. Industrial production of the solution SBR was first proposed by the U.S. company, Phillips, in batch process and Firestone company in continuous process. Since the solution SBR is superior to the emulsion SBR in mechanical properties, rolling resistance, wet or ice skid resistance, the solution SBR is widely used by the automotive industry and in other rubber products. With the increasingly requirements for cars with low fuel economy, demands on tire rubber materials for such characteristic requirements are also increased. Conjugated diene-based rubbers with low rolling resistance, excellent wear resistance, and balanced wet-skid resistance led to increasing demand by the automobile industry.
On the other hand, the industry has proposed to add silica compounds or mixture of silica compounds and carbon black as a reinforcing agent to a rubber composition. Tire treads containing compounds with mixture of silica and carbon black or silica compounds are favorable with low rolling resistance and wet skid resistance.
Of the related technical publications, U.S. Pat. No. 4,185,042 discloses a coupling agent used for SBS block copolymer. Lithium-containing polymer reacts with the coupling agent (i.e., epoxy-R2—Si(OR)2R1), thereby obtaining the SBS block copolymer with the coupling ratio>90% and without Si—OR group presented in the SBS block copolymer.
U.S. Pat. No. 5,015,692 discloses an amino silane coupled styrene-butadiene rubber. The chain ends containing lithium of the—diene polymer molecules react with the coupling agent (i.e., R1R2R3—Si—(CH2)n—N—R4R5) to modify the styrene-butadiene rubber. However, there is not any disclosure of modification of the SBR with alkoxysilane group containing compounds.
U.S. Pat. No. 5,219,938 discloses a two-stage modification process. By using two kinds of modifiers, the chain ends containing lithium of—diene polymer molecules react with coupling agents RnSiCl4-n or RnSnCl4-n to perform first modification of the styrene-butadiene rubber, and then with the coupling agent (R5R6R7—Si—(CH2)n—N—R8R9) to perform second modification of the styrene-butadiene rubber.
U.S. Pat. No. 5,665,812 discloses modification of the SBR with compounds containing epoxy and alkoxysilane groups. The styrene-butadiene rubber is modified with epoxidized alkoxysilane compounds (e.g., Y—R1—Si(OR2)3).
U.S. Pat. No. 7,288,594 discloses a two-step modification of lithium-containing styrene-butadiene rubber by using two different kinds of silane compounds. In addition, U.S. Pat. No. 7,807,747 discloses a two-step modification of lithium-containing styrene-butadiene rubber by using the same silane compound.
However, none of the above-mentioned related art discloses modification of conjugated diene rubbers to improve storage stability. In practical applications, improvement of storage stability of the conjugated diene rubber, maintaining high reactivity with the silica compounds and sustaining better physical properties are demanded. The conjugated diene rubber and the compositions/composite using the conjugated diene rubber of the present invention are used for tires, soles, flooring materials, vibration isolating materials, etc., and are particularly suitably used for tires, thereby enhancing the tire treads with low rolling resistance and high wet /ice skid resistance resulted in better steering stability and reliability.